In recent years, stereoscopic image display devices configured to display a left-eye image and a right-eye image on a display to achieve stereoscopic vision have been becoming increasingly widespread. In stereoscopic vision, a positional displacement of corresponding points between the left-eye image and the right-eye image is called disparity. It is known that a marked increase in disparity in the divergence direction or convergence direction makes it difficult to attain stereoscopic vision.
When a person observes a left-eye image and a right-eye image, depth is perceived by means of binocular retinal disparity. Binocular retinal disparity is the difference between images of an external object projected onto the right and left retinas. In order to detect binocular retinal disparity, it is necessary to determine which points on the retinal images of the two eyes are produced by a single object. NPL 1 introduces models of a mechanism for detecting retinal disparity.
In one such model, on the basis of the concept that a luminance edge in the right and left images is a fundamental feature of binocular correspondence, close points having almost the same contrast polarity and orientation are associated with each other. Another model is introduced in which a plurality of spatial filters having different orientation selectivities and sizes are applied to each of the right and left images, vectors formed by the outputs of these spatial filters are used to distinguish local structures at given positions in the image from each other, and the points of highest similarity between vectors at the respective positions on the right and left eyes are associated with each other.
PTL 1 discloses a stereoscopic TV apparatus in which a block in a left image and a block in a right image are associated with each other to adjust the amount of binocular disparity. In the disclosed stereoscopic TV apparatus, a correlation Corr(i, j) between a block in the left image and a block in the right image is calculated using Expression (1) as follows:
                    [                  Math          .                                          ⁢          1                ]                                                                      Corr          ⁢                                          ⁢                      (                          i              ,              j                        )                          =                              ∑                          k              =              1                                      n              ×              n                                ⁢                                          ⁢                                                                                  G                  L                                ⁡                                  (                                                            X                      k                                        ,                                          Y                      k                                                        )                                            -                                                G                  R                                ⁡                                  (                                                                                    X                        k                                            -                      i                                        ,                                                                  Y                        k                                            -                      j                                                        )                                                                                                    (        1        )            
where GL(Xk, Yk) and GR(Xk, Yk) are luminance values at the coordinates (Xk, Yk) in the left image and the right image, respectively, n is the number of horizontal and vertical pixels in the respective blocks in the left image and the right image (the total number of pixels in the blocks is given by n×n), and i and j are the amounts of translation of a block in the horizontal and vertical directions, respectively.
In the stereoscopic TV apparatus, the amounts of translation i and j between which the correlation Corr(i, j) is minimum are searched for, and accordingly a block in the right image is associated with a block in the left image. Specifically, in the stereoscopic TV apparatus, the block in the right image having the most similar luminance value to a block in the left image is searched for, and these blocks are set as corresponding blocks.